JPH0450880A - Developing device for electrophotographic device - Google Patents

Abstract

PURPOSE:To always obtain a proper image density by carrying out the correcting of a toner electrifying quantity, not only for a change in environmental humidity, but also for the utilization time of a developer. CONSTITUTION:This developing device is provided with a toner supplying part 30 housing a tow-component developer composed of toner and a carrier, and supplying the toner to the surface of an image carrier where an electrostatic latent image is formed, a toner replenishing part 40 replenishing the toner to the toner supplying part 30, and a toner density detecting means 36 detecting the density of the toner inside the toner supplying part. Then, a signal from the toner density detecting means 36 is compared with a reference value. When the density of the toner is reduced, the toner is replenished from the toner replenishing part 40 to the toner supplying part 30. Then, the reference value is corrected b the environmental humidity and the utilization time of the developer. In other words, when the environmental humidity is made high, or the utilization time of the developer is prolonged, the density of the toner is reduced, and the toner electrifying quantity is maintained. Thus, the density of an image can be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device for an electrophotographic apparatus that uses a two-component developer in which a toner and a carrier are mixed as a developer.

(Prior Art) Conventionally, in an electrophotographic apparatus, a charged photoreceptor drum is irradiated with a light source to form an electrostatic latent image on its surface.
After toner is applied to the electrostatic latent image and developed, the toner image is transferred to a recording medium.

In the case of a developing device that uses a two-component developer consisting of toner and carrier, the mixing ratio of toner and carrier, that is, the toner density, is controlled to a predetermined value to optimize the image density formed on the recording paper. There is. In this case, the toner concentration of the developer can be detected by using a coil and detecting the magnetic permeability that changes depending on the amount of magnetic carrier in the developer, or by measuring the light reflectance of the developer using a photosensor. A method of detection is known.

FIG. 7 is an explanatory diagram of the principle of a detection sensor that detects toner concentration based on magnetic permeability, and FIG. 8 is an explanatory diagram of the operation of FIG. 7.

In the figure, 1 is a detection sensor, and this detection sensor 1
is equipped with a primary coil 2 that inputs a reference waveform and a secondary coil, and the secondary coil includes a detection coil 4 that has a magnetic carrier in the developer 3 as part of a magnetic circuit, and a ferrite core 5 that is magnetically connected to the magnetic carrier. It has a coil 6 that is included as part of the circuit. Then, when the inductance M of the detection coil 4 changes according to the amount of magnetic carrier in the developer 3,
A phase difference between the detected waveform A+B occurs due to the difference with the inductance M2 of the coil 6 serving as a reference. By measuring this phase difference, toner concentration can be detected.

Therefore, the reference waveform C on the negative side and the detected waveform A1B on the secondary side synthesized by bridge coupling are input to the phase detector 7 and compared. The larger the phase difference of the detected waveform A-I-B with respect to the reference waveform C, the more time the signal after comparison shows a high potential of 1, that is, the detected waveform A+ on the secondary side.
Since the time when the input on the B side is at a high potential and the input on the reference waveform C side is at a low potential is longer, this can be integrated and extracted as a change in the DC voltage signal.

However, in the case of the detection sensor having the above configuration, even if the toner density can be adjusted to a constant value, the image density will change if the amount of charge held by the charged toner, that is, the amount of toner charge changes.

FIG. 9 is a diagram showing the relationship between toner charge amount and image density. The plots are based on data obtained by changing only the amount of charge while keeping the toner concentration constant.

As shown in the figure, even if the toner density of the developer is kept constant, the image density changes due to a change in the toner charge amount. That is, when the toner charge amount is small, the image density becomes high, and when the toner charge amount is large, the image density decreases.

Incidentally, the amount of toner charge in the developer changes depending on various factors. For example, even if the toner concentration and developer agitation conditions are constant, the toner charge amount will vary greatly if the environmental humidity changes.

FIG. 10 is a diagram showing the relationship between humidity and image density.

As shown in the figure, it can be seen that when the environmental humidity (relative humidity) becomes 50% or more, the image density increases rapidly. This is because the toner charge amount decreases in a high humidity environment.

Therefore, a developing device that can prevent the image density from changing due to humidity has been proposed (Japanese Patent Laid-Open No. 58-3
(See Publication No. 3271).

FIG. 11 is a circuit diagram of the image density adjustment device. In the figure, S is a toner concentration sensor, 8 is a comparator, 9 is a processor, 10 is a toner replenishment circuit, and HD is a humidity sensor. In the image density adjusting device configured as described above, the reference voltage of the (+) input of the comparator 8 is changed in response to the change in the toner charge amount depending on the environmental humidity. As the reference voltage for this purpose, a voltage obtained by dividing the power supply voltage (2) by a resistance circuit including the humidity sensor HD is used.

(Problem to be Solved by the Invention!!) However, in the developing device of an electrophotographic apparatus having the above configuration, the amount of toner charge varies greatly depending not only on the environmental humidity but also on the usage time of the developer.

FIG. 12 is a diagram showing the relationship between toner concentration and toner charge amount.

The figure shows the relationship between the toner concentration and the toner charge amount when the developer is in the initial state of use and when the developer is used for 50 hours. That is, it can be seen that when the developer is used for 50 hours, the toner charge amount decreases by about 2 μc/H.

Therefore, if a developer is used for 50 hours with a toner density set so that an appropriate image density can be obtained in the initial state of use, the amount of toner charge will be insufficient and the image density will be excessive, causing "background fog." Resulting in.

The present invention solves the above-mentioned problems with the developing device of the conventional electrophotographic apparatus, and corrects the toner charge amount not only in response to changes in environmental humidity but also in accordance with the usage time of the developer, so that the amount of toner charge is always appropriate. An object of the present invention is to provide a developing device for an electrophotographic apparatus that can obtain a high image density.

(Means for Solving the Problems) To this end, the developing device of the electrophotographic apparatus of the present invention contains a two-component developer consisting of toner and carrier, and the surface of the image bearing member on which the electrostatic latent image is formed. The toner supply section includes a toner supply section that supplies the toner to the toner supply section, and a toner supply section that supplies toner to the toner supply section.

A toner concentration detection means for detecting the toner concentration in the toner supply section is provided, and a signal from the toner concentration detection means is compared with a reference value to determine the amount of toner supplied from the toner supply section to the toner supply section. It's about to be controlled.

The above-mentioned reference value is corrected based on the environmental humidity and the usage time of the developer to eliminate changes in the toner charge amount.

Therefore, a humidity detection means for detecting the environmental humidity and a use time detection means for detecting the use time of the developer are provided.

(Function) According to the present invention, there is provided a toner supply unit that accommodates a two-component developer consisting of toner and a carrier and supplies the toner to the surface of an image carrier on which an electrostatic latent image is formed; and a toner concentration detection means for detecting the toner concentration in the toner supply section, and compares the signal from the toner concentration detection means with a reference value to determine if the toner concentration has decreased. Then, toner is supplied from the toner supply section to the toner supply section.

The reference value for controlling the amount of toner replenishment at this time is corrected based on the environmental humidity and the usage time of the developer. That is, as the environmental humidity increases or the developer is used for a long time, the toner charge amount decreases, so the toner charge amount can be maintained by reducing the toner concentration accordingly.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a control circuit diagram of a developing device of an electrophotographic apparatus showing an embodiment of the present invention, FIG. 2 is a schematic diagram of a developing device of an electrophotographic device showing an embodiment of the present invention, and FIG. 1 is a schematic diagram of an electrophotographic apparatus to which a developing device is applied.

In FIG. 3, 11 is a cylindrical photoreceptor drum (image carrier) rotating in the direction of arrow R; 12 is the photoreceptor drum 11;
13 is an LED head in which LED elements are arranged in the axial direction of the photosensitive drum 11; 14;
1 is a print control unit that controls the driving of the LED head 13;
A developing device 5 transfers toner onto the surface of the photosensitive drum 11 to visualize the electrostatic latent image. Further, reference numeral 16 denotes a paper feed cassette 7 for storing the transfer paper P, and 17 a paper feed roll for taking out the transfer paper P one by one from the paper feed cassette 16.
8 is a registration roll that adjusts the conveyance timing of the transfer paper P; 19 is a transfer charger that transfers the toner on the photoreceptor drum 11 to the transfer paper P; 20 is a transfer charger that transfers the transfer paper P to the photoreceptor drum 1;
A separation static eliminator is separated from 1, and 21 is a fixing device. Note that 22 is a static elimination lamp for erasing an electrostatic latent image that is no longer needed on the photoreceptor drum 11, and 23 is a cleaning section. The electrophotographic apparatus having the above configuration operates as follows.

First, the photosensitive drum 11 rotates in the direction of arrow R, and its surface is uniformly charged by the charger 12. When the photoreceptor drum 11 charged as shown in FIG. is formed. This electrostatic latent image reaches a position facing the developing device 15, where toner is applied and development is performed.

Thereafter, the toner image formed on the photosensitive drum 11 reaches a position facing the transfer charger 19. On the other hand, the registration roll 18 conveys the transfer paper P between the photoreceptor drum 11 and the transfer charger 19 in synchronization with the timing of the movement of the toner image, and due to the action of the transfer charger 19, the photoreceptor drum ll
The upper toner image is transferred onto transfer paper P. The transfer paper P onto which the toner image has been transferred is separated from the photoreceptor drum 11 by a separation static eliminator 20 and conveyed to a fixing device 21 . Fuser 2
1, a fixing roller kept at a constant temperature by a fixing heater heat-fixes the toner image onto the transfer paper P, and then the transfer paper P is discharged outside the machine.

Incidentally, unnecessary charges on the surface of the photoreceptor drum 11 are erased by a charge eliminating lamp 22, and toner remaining on the photoreceptor drum 11 without being transferred to the transfer paper P is removed by a cleaning section 23. Thereafter, the photosensitive drum 11 is uniformly charged again by the charger 12 in preparation for the next image exposure, and the process proceeds to the next image forming process.

Next, the developing device 15 will be explained based on FIG. 2.

As shown in the figure, the developing device 15 contains a two-component developer consisting of toner and carrier, and transfers the toner to the photoreceptor drum 1.
1 and a toner replenishing section 40. The toner supply unit 30 includes a storage tank 31 that stores toner and carrier, a sleeve 32 for conveying the toner in the storage tank 31 to the photosensitive drum 11, a magnet roll 33 provided in the sleeve 32, A regulating member (blade) 34 that is disposed near the sleeve 32 and regulates the thickness of the developer held on the sleeve 32, a stirring roll 35 that stirs the toner and carrier in the storage tank 31, and a storage It has a toner concentration sensor 36 that detects the toner concentration in the tank 31.

The toner supply unit 40 is disposed above the toner supply unit 30, and includes a toner supply tank 41 that accommodates a toner supply cartridge and a toner supply unit 3 of the toner supply tank 41.
It has a replenishment roller 43 for replenishing toner. In the toner supply unit 30, when the toner inside the supply tank 31 is consumed, the replenishment roller 43 rotates and the toner supplied to the replenishment tank 31 is mixed with the carrier by the stirring roll 35.

Further, the sleeve 32 is made of a cylinder made of a non-magnetic material such as aluminum, and rotates in the direction of arrow Q. A magnet roll 33 made of a multi-pole fixed magnet is disposed inside the sleeve 32 to attract the developer to the surface of the sleeve 32 . As the carrier in the developer, a carrier mainly composed of a magnetic material having a particle size of 20 to 200 μl and coated with a resin is used, and as a toner, a carrier mainly composed of a resin is used.

Next, the operation of the developing device 15 will be explained.

In the developing device 15, when the stirring roller 35 stirs the toner and carrier, the toner is charged by friction. When the developer is conveyed on the sleeve 32 and passes through the gap with the regulating member 34, it is formed into a spike shape of a certain height and is applied to the photoreceptor drum 11.
Sent to the intermediary department. Then, the spikes of the developer are brought into contact with the surface of the photoreceptor drum 11, and a portion of the toner is transferred to the photoreceptor drum 11 due to the electrostatic attraction between the electrostatic latent image on the surface of the photoreceptor drum 11 and the charge of the toner. The toner is transferred to the surface and adheres to the electrostatic latent image.

As described above, the spikes of developer are regulated to a certain height by the regulating member 34, but the developer that is removed by hitting the regulating member 34 collapses when it reaches a position where it is not affected by the magnetic field of the magnet roll 33. It falls and is collected in the lower part of the storage tank 31. The collected developer is mixed and stirred by the stirring roller 35 together with the toner replenished by the rotation of the toner supply roll 43, and then the sleeve 3
2 and subjected to development.

Further, the developer is mixed between the stirring roller 35 and the toner concentration sensor 36.
When the developer passes through the interval, the toner concentration sensor 36 detects the toner concentration in the developer. When the toner concentration is detected, a toner concentration control circuit, which will be described later, replenishes a predetermined amount of toner using a toner replenishment roll.

Next, regarding the toner concentration control of the developing device 15, the first
This will be explained based on the diagram.

As shown in the figure, in the toner concentration control circuit, the output of the toner concentration sensor 36 is the output of the comparator 51 (
−) input, and the reference voltage Vc is input to the (+) input of the comparator 51. In addition, the comparator 51
The output of the processor 58 is connected to the input port of the processor 58, and the output port of the processor 58 is connected to the toner replenishment circuit 59 which rotates the drive motor of the replenishment roller 43 of the toner replenishment section 40.
connected to. Further, a developer use time memory element (EEFROM) 37 is connected to the input/output port of the pro sensor 58. Further, the output port of the processor 5 has an inverter IC 57 and a resistor 56 connected in series, and the resistor 56 is connected to the (+) input of the comparator 51.

FIG. 4 is a diagram showing the relationship between toner concentration and toner charge amount for explaining the operation of the developing device of the electrophotographic apparatus of the present invention.

Assuming that the toner concentration of the developer is 4% in the initial state of use, in order to obtain the same amount of charge on the toner at that time with the developer after 50 hours of use, the toner concentration needs to be 3%. It is shown that.

FIG. 5 is a relationship diagram of the toner concentration, the output voltage of the toner concentration sensor, and the reference voltage VC. a is the reference voltage Vc when the developer usage time is 0 hours, and a2 is the reference voltage V when the developer usage time is 50 hours. It is. The humidity conditions at this time were both 50%.

As shown in the figure, the toner concentration sensor output increases as the toner concentration decreases. Therefore, when the toner charge amount decreases as the developer usage time increases, if the reference voltage Vc is increased from a to a2 accordingly,
The toner charge amount in FIG. 4 is constant.

Here, as the humidity detection element 52, Huumilite (
The reference voltage Vc is increased by using a sensor whose resistance value decreases as the humidity increases, such as a ceramic humidity sensor H104 (trade name) or a ceramic humidity sensor H104 (trade name).

Further, as the developer use time storage element 37, EEFR
Use OM. Then, the developer usage time storage element 3
Information proportional to the rotation time of the motor that drives the stirring roll 35 of the developing device is written in the block 7 by a block 58.

FIG. 6 is an operation flowchart for setting the reference voltage Vc.

Step (2) The information on the developer usage time written in the developer usage time storage element 37 by the processor 58 is read out.

Step ■ Compare with the set time.

Step (2) If the value exceeds the set time, the output of the inverter IC 57 is set to H'' level and the reference voltage Vc is increased.As a result, the toner density decreases and the decrease in toner charge amount due to developer use time is corrected.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described in detail above, according to the present invention, a two-component developer consisting of toner and a carrier is accommodated, and the toner is applied to the surface of the image bearing member on which an electrostatic latent image is formed. It has a toner supply section that supplies toner, a toner supply section that supplies toner to the toner supply section, and a toner concentration detection means that detects the toner concentration in the toner supply section, and a signal from the toner concentration detection means. When the toner concentration decreases compared to a reference value, toner is replenished from the toner replenishing section to the toner supplying section.

Since the reference value for controlling the amount of toner replenishment at this time is corrected based on the environmental humidity and the usage time of the developer, the amount of toner charge can always be kept constant. Therefore, the image density can be kept constant, and "background fog" and image quality deterioration will not occur.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of a developing device of an electrophotographic apparatus showing an embodiment of the present invention, FIG. 2 is a schematic diagram of a developing device of an electrophotographic device showing an embodiment of the present invention, and FIG. A schematic diagram of an electrophotographic apparatus to which the developing device is applied, FIG. 4 is a diagram showing the relationship between toner concentration and toner charge amount for explaining the operation of the developing device of the electrophotographic apparatus of the present invention, and FIG. 5 is a diagram showing the toner concentration, 6 is an operation flowchart for setting the reference voltage Vc, and FIG. 7 is a diagram explaining the principle of the detection sensor that detects toner concentration by magnetic permeability. Figure 8 is an explanatory diagram of the operation in Figure 7;
Figure 9 is a relationship diagram between toner charge amount and image density, Figure 1O is a relationship diagram between humidity and image density, Figure 11 is a circuit diagram of the image density adjustment device, and Figure 12 is a relationship diagram between toner density and toner charge amount. It is a diagram. 36... Toner concentration sensor, 37... Developer use time storage element, 43... Supply roller, 51... Comparator, 52... Temperature detection element, 56... Resistor, 5
7... Inverter IC158... Processor, 59
...Toner supply circuit. Fig. 2 Ji 1 Semi 1 Sho ru e θ Bushido mortar Ten Btp Moving r no 0 - Temat Fig. 6 Fig. 7 Operation gate Fig. 8 Toner flat charge amount (!'%) yx degree (% ) Moonlit degree and!, Image luL" Sekiφ square diagram Figure 10 + V Image density 4 river police station Q circuit diagram Figure 11

Claims (1)

[Scope of Claims] (a) a toner supply unit containing a two-component developer consisting of toner and carrier and supplying the toner to the surface of the image bearing member on which an electrostatic latent image is formed; (b) a toner replenishing section that replenishes toner to the toner supply section; (c) a toner concentration detection means that detects the toner concentration in the toner supply section; and (d) a signal from the toner concentration detection means that is compared with a reference value. , a means for controlling the amount of toner supplied from the toner replenishing section to the toner supplying section; (e) a humidity detecting means for detecting environmental humidity; and (f) a use time detecting means for detecting the use time of the developer. (g) A developing device for an electrophotographic apparatus, comprising a correction device for correcting the reference value based on the outputs of the humidity detection device and the usage time detection device to eliminate changes in toner charge amount.